In the last 120 years in Perth there has never been a September as cold as this one. We know that thanks to Chris Gillham, who has been tracking Western Australian weather in detail for years at WAClimate.net.

The headline in The West Australian today was Perth shivers through it’s coldest ever September. For some reason (I can’t think why) the extreme weather journalists did not mention climate change (has that ever happened on a hottest ever record story?). It’s so unusually cold here that wheat farmers, only weeks away from harvest*, are struggling with frost damage on crops. They are making snowmen from the frosts. It is supposed to be rapidly heating up but it is three degrees below normal.

Given the freak weather, Will Steffen immediately announced that“This is a prelude to a disturbing future. And it’s only going to get worse if we don’t address climate change.” No. Wait. Scratch that. That was South Australia, where one bad storm was caused by coal fired electrons. A record cold month is just weather.

Curiously, The Bureau of Meteorology(BOM) announced it was the coldest ever September for Perth since 1994 when records started at Mt Lawley, and the coldest at Perth Airport since records started there in 1944. But it took an unpaid data-aficionado to discover that it was actually the coldest since 1897 at the Perth Regional Office (see the “grains of salt” about this at the end of the post). And that applies to the super-spiffy-adjusted ACORN dataset which goes back to 1910. A coldest “ever” record.

Chris Gillham writes that “This September wasn’t just a bit cold in Perth. It was very cold compared to almost all Septembers ever recorded in Stevensons.” The mean was a record because of the unusually cool minima, not the maxima. Perth Airport’s coldest September since 1944 smashed the previous mean temp record of 1968 by 0.73C and, even with cooling adjustments since 1910, this September in ACORN was 0.48C colder than the previous homogenised record in 1919.

By the way, I note tomorrow there is a severe weather warning in SW WA with gusts of up to 125 km per hour. This is a Category 4 Grid Destroying Gust. Hope and pray that we still have electricity tomorrow.

A million square kilometers of cooler ocean

Chris Gillham points out there’s a big cold blob in the ocean around South and West Australia that just might have something to do with the cold weather. (See the sea-surface temperature maps below).

The Great Southern Cold blob may also have something to do with those South Australian storms.

Phill (also of the unauthorized BOM audit group) sends in with a graph of the SST anomalies for today from earth.nullschool.net “You can see that it is hot (over 2.5C in places) along the North West and North Coast and Cold along the South and South West Coasts (over 2C below average in places). All that extra heat across the North has been sending NW cloud bands across the continent and periodically interacting with the cold southern air which wedges underneath and causes nasty weather.”

What do records really mean? (Not much)

Gillham has gone through the full history of the site moves of the Perth Regional Office which started in 1897. He goes into glorious detail as it shifts from Kings Park, to the city then to Mt Lawley (away from the river). These are quite different locations. Bear in mind with all these “records” that there are no perfect datasets and not a lot of meaning a tenth of a degree recorded in two different places 120 years apart. Though, the BOM spent so much effort on the world class ACORN hyper-adjusted series, which is supposed to overcome all the site moves by homogenizing places hundreds of kilometers away, and yet they somehow didn’t notice the long cold record that was the coldest since ACORN records started in 1910…

Max:This month was the 18th Coldest September max Perth Metro and RO raw since 1897

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*For Northern Hemisphere readers, in WA our summers are so hot and dry that crops are planted in the fall, and grown through our mild wet winters, where frosts are rare. They get harvested in November just before summer when farm equipment and car seat-belts became branding irons.